Issue |
A&A
Volume 380, Number 1, December II 2001
|
|
---|---|---|
Page(s) | 212 - 220 | |
Section | Interstellar and circumstellar matter | |
DOI | https://doi.org/10.1051/0004-6361:20011369 | |
Published online | 15 December 2001 |
Diffraction-limited speckle interferometry and modeling of the circumstellar envelope of R CrB at maximum and minimum light
1
Max-Planck-Institut für Radioastronomie, Auf dem Hügel 69, 53121 Bonn, Germany
2
Special Astrophysical Observatory, Nizhnij Arkhyz, Zelenchuk region, 35147 Karachai-Cherkesia, Russia
3
Crimean Astrophysical Observatory, Nauchny, 98409 Crimea, Ukraine, and Isaac Newton Institute of Chile, Crimean Branch, Russia
4
Sternberg Astronomical Institute, Universitetskii pr. 13, 119899 Moscow, Russia
Corresponding author: K. Ohnaka, kohnaka@mpifr-bonn.mpg.de
Received:
31
January
2001
Accepted:
27
September
2001
We present the first speckle interferometric observations of
R CrB,
the prototype of a class of peculiar stars which undergo
irregular declines in their visible light curves.
The observations were carried out with the 6 m telescope at the
Special Astrophysical Observatory
near maximum light (, 1996 Oct. 1) and at minimum light
(
, 1999 Sep. 28).
A spatial resolution of 75 mas was achieved in the K-band.
The dust shell around
R CrB is partially resolved, and the visibility is approximately
0.8 at a spatial frequency of 10 cycles/arcsec.
The two-dimensional power spectra obtained at both epochs
do not show any significant deviation from circular symmetry.
The visibility function and spectral energy distribution obtained
near maximum light can be simultaneously fitted with a model
consisting of the central star and an optically thin dust shell with
density proportional to r-2. The inner boundary of the shell is
found to be 82
(19 mas) with a temperature of 920 K.
However, this simple model fails to simultaneously reproduce
the visibility and spectral energy distribution obtained at minimum light.
We show that this discrepancy can be attributed to thermal
emission from a newly formed dust cloud.
Key words: stars: carbon / stars: circumstellar matter / stars: mass-loss / stars: individual: R CrB / stars: variables: general / infrared: stars
© ESO, 2001
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